1. Field of the Invention
This invention relates to an armature winding for a dynamoelectric machine having a double-layer concentric-wound coil arrangement or a lap winding arrangement and a method of making such an armature winding.
2. Description of the prior art
FIG. 62 is a development diagram of a conventional arrangement of a concentric-wound type armature winding of AC machinery, particularly, three-phase induction motors. The shown armature winding is of a three-phase, four-pole, 48-slot type. FIG. 63 shows an arrangement of coils of the armature winding disposed in slots. Each dotted line in FIG. 62 shows a coil side which is inserted into the coil to overlap with the upper side (open side) thereof. Each solid arc in FIG. 63 shows an coil end of the coil and each black dot shows the coil side. Numerals 1 to 48 designate slot numbers, which will be hereinafter presented as #1 to #48. Reference symbols U1, U2, U3 and U4 designate pole windings of a phase U, reference symbols V1, V2, V3 and V4 pole windings of a phase V, and reference symbols W1, W2, W3 and W4 pole windings of a phase W.
Only one coil is inserted in each of slots #1 and #12 in the first pole winding U1 of the phase U so that concentric-wound coils are composed, whereas a coil is inserted in each of slot pairs of #2 and #11, and #3 and #10 together with another coil of another phase (coils of windings V4 and W1 respectively) so that concentric-wound coils are composed. Usually, the coils inserted in the slot pair of #2 and #11 and in the slot pair of #3 and #10 have the same number of turns, which number is a half of that of the coil inserted in the slot pair of #1 and #12. All the other concentric-wound coils also have the above-mentioned double-half turns relation in the number of turns.
Publication No. 51-28125 (1976) of a Japanese examined patent application discloses an arrangement of the armature winding as shown in FIG. 64. Publication No. 60-36698 (1985) of a Japanese examined patent application discloses an arrangement of the armature winding as shown in FIG. 65. Neither publication describes the number of turns of each coil in detail, but, usually, the number of turns of the coil when the same is inserted in the slot together with a coil of another phase is a half of that when only the coil is inserted in the slot. Thus, all the coils generally have the double-half turns relation.
The magnetomotive force waveform of an armature winding is nonsinusoidal when the coils in the respective slots have the double-half turns relation. The nonsinusoidal magnetomotive force waveform results in a large number of harmonics, which disadvantageously cause a reduction in the efficiency and power factor of the motor or an increase in the noise due to electromagnetic vibration.
For the purpose of overcoming the above-described disadvantage, the prior art has provided an arrangement of sinusoidal winding wherein the number of turns of the coil is changed from slot to slot so that the magnetomotive force distribution approximates a sinusoidal wave. For example, publication No. 6-261479 (1994) of a Japanese unexamined patent application discloses an arrangement of armature winding composed into a sinusoidal, double-layer, concentric-wound winding. Referring to FIG. 67, the disclosed arrangement will be described. FIG. 67 is a development diagram of an armature winding of a three-phase, four-pole, 48-slot type with two parallel electrical paths being formed between external terminals U and X. When q is the number of slots in each pole in each phase, q=48/(3.times.4)=4. Each pole winding in each phase comprises four continuous coils arranged concentrically so that each pole winding is composed into a double-layer concentric-wound winding. The four coils are connected to one another so that a pole winding is formed. Thus, as a whole, the armature winding comprises twelve concentric-wound coils which are pole windings U1, U2, U3 and U4 of phase U, pole windings V1, v2, V3 and V4 of phase V, and pole windings W1, W2, W3 and W4 of phase W. The coils are inserted in the slots #5 to #16, and the coil pitches of the pole windings are 11, 9, 7, and 5 respectively. For example, a first pole winding U1 of phase U is composed of a coil inserted in the slots #5 and #16 at the pitch of 11, a coil inserted in the slots #6 and #15 at the pitch of 9, a coil inserted in the slots #7 and #14 at the pitch of 7, and a coil inserted in the slots #8 and #13 at the pitch of 5, all the coils being sequentially laid one upon another. Regarding each of the other poles of phase U and each of the other phases, four coils are interconnected at the coil pitches of 11, 9, 7 and 5 in the same manner as described above.
FIG. 68 illustrates the number of turns of the coil in each slot. It is noted that FIG. 68 shows only the arrangement of the coils inserted in the respective slots but shows nothing as to which coils serve as the upper or lower coils. The number of turns of each slot-inserted coil in the shown arrangement is the same as in the prior art, but the number of coils in each phase is twice as large as that in the prior art. For example, as shown in FIG. 68, the first pole winding U1 of the phase U is distributed in slots #5 to #8 and in slots #13 to #16, and the number of turns is changed sequentially from 28 in slot #5 to 21 in slot #6, 13 in slot #7 and 5 in slot #8 and from 5 in slot #13 to 13 in slot #14, 21 in slot #15 and 28 in slot #16, whereby the winding U1 is composed into a concentric-wound winding. Further, the second pole winding U2 of the phase U is distributed in slots #17 to #20 and in slots #25 to #28, and the number of turns is changed sequentially from 28 in slot #17 to 21 in slot #18, 13 in slot #19 and 5 in slot #20 and from 5 in slot #25 to 13 in slot #26, 21 in slot #27 and 28 in slot #28, whereby the winding U2 is composed into a concentric-wound winding. Thus, the numbers of turns of the coils are changed sequentially from 5 in slot #1 to 13 in slot #2, 21 in slot #3, 28 in slot #4, 28 in slot #5, 21 in slot #6, 13 in slot #7 and 5 in slot #8 so that the magnetomotive force can be rendered approximately sinusoidal.
Since the above-described arrangement is composed into the double-layer, concentric-wound type, the total numbers of turns of upper and lower coils inserted in slots #1 to #4 in FIG. 68, for example, are 33, 33, 34 and 34. Thus, the total number of turns of coils inserted in each slot is approximately uniform, which shows that the sectional area of each slot is effectively utilized.
The number of turns of each coil inserted in each slot is determined so that the magnetomotive force produced by the winding is rendered approximately sinusoidal and so that the high frequency winding factor approximates zero. For example, this is described in detail in "Study on the theory of abnormal phenomena in induction motors," by Chukichi Okawa in "Shibaura Review" Volume 8, 1934. FIG. 69 illustrates an arrangement of upper and lower coils and the number of turns of each coil in the armature winding as shown in FIG. 68.
FIGS. 70A and 70B show distribution of the magnetomotive force in the case of the sinusoidal winding and in the case of a nonsinusoidal winding respectively. FIG. 71 shows winding factors of the sinusoidal winding shown in FIG. 70A and those of the nonsinusoidal winding shown in FIG. 70B. As obvious from these figures, the sinusoidal winding can render the magnetomotive force approximately sinusoidal and reduce the high frequency winding factor to a large extent.
FIG. 72 illustrates the arrangement of upper and lower coils inserted in each slot and the number of turns of each coil with respect to the winding arrangement shown in FIG. 68. First, all the pole windings U1 to U4 of phase U are inserted into the slots to serve as lower coils. All the pole windings V1 to V4 of phase V are then inserted into the slots to serve as lower coils. Finally, all the pole windings W1 to W4 of phase W are inserted into the slots to serve as upper coils, so that the double-layer, concentric-wound winding is provided. Since all the windings of each phase can be simultaneously inserted into the slots, the inserting work can be simplified and the windings can be inserted into the slots by a coil inserting machine. Consequently, the above-described winding arrangement can achieve the same effect of sinusoidal winding as in a lap winding, and insulators can be mechanically inserted into the slots. Thus, in the above-described arrangement, the numbers of turns of the coils inserted in each slot is changed so that the magnetomotive force produced by the winding is rendered approximately sinusoidal, whereby the motor characteristics can be improved.
In the conventional concentric-wound windings as shown in FIGS. 62 and 66, however, all the coils inserted in each slot have the double-half turns relation in the number of turns. Accordingly, since the magnetomotive force cannot be rendered sinusoidal, a large number of harmonics result in reduction in the efficiency and power factor of the motor or an increase in the noise due to electromagnetic vibration.
The double-layer concentric-wound winding employing the sinusoidal winding as shown in FIG. 67 overcomes the above-described drawbacks. However, the coils belonging to different phases are inserted in all the slots #1 to #48 although the differences in the number of coil turns among the slots are small, as is obvious from FIG. 72. Accordingly, the insulators need to be inserted into all the slots so that the coils belonging to the different phases are insulated from each other, which results in increase in the number of steps in the assembly of the winding.
Furthermore, in some slots, the number of turns of the upper coil quite differs from that of the lower coil in the armature winding shown in FIG. 67. These slots include slots #1, #4, #5, #8, #9, #12, #13, #16, #17, #20, #21, #24, #25, #28, 29, #32, #33, #36, #37, #40, #41, #44, #45 and #48. In each of these slots, one coil is wound five turns, whereas the other coil is wound 28 turns. Accordingly, since the dimensions of the insulator inserted into each slot need to be varied, a large number of different types of insulators need to be provided. Furthermore, the coil and the insulator are sometimes settled improperly in the slot when the number of turns of the coil first inserted into the slot is smaller. Consequently, the subsequent manual or mechanical inserting of the coil is rendered difficult or the insulator having inserted in the slot is displaced, whereupon the quality of products is lowered. Additionally, since the pole windings have different dimensions respectively, coil formers the number of which is equal to that of the pole windings are disadvantageously required.